No display on MPGuino LCD, just backlight

[dcb]

Did you check for cross wiring? I.e. put the ohmeter on lcd 16, and make sure there is no connections where there shouldn't be?


Just for comparison, I did and most of the connections were separated by at least a megaohm, except the following:

LCD pins 1,5,16 all connected.

LCD pins 2 and 3 were seperated by about 10k ohms (shrug).

notes:
unit unplugged
I put ground on LCD 1, then touched positive probe to 2, then 3 ... 16 and noted ohm readings.

Then I put ground on LCD 2, then touched positive probe to 3, then 4 ... 16 and noted ohm readings.

Then I put ground on LCD 3, etc.

[Wingmn]

I checked for cross wiring. None present except the ones that are suppose to be.

1, 5, 16 are all connected.

I'm going to jumper all signal lines straight from the Atmega to the LCD pads when I get some time..

I'll do it 1 at a time so if I fix it I will not have to do all of them.. shouldn't be too bad, since all 16 pins are not signal lines.. I won't do power or ground, and I know there are several that aren't used.

[Wingmn]

I think I found the problem.

I desoldered the LCD again in preperation to jumper atmega pins to the LCD pads.

I looked at the back of LCD and noticed Pad 3 had some missing gold on the back side of the pad - here's a picture.

I did some continuity checks between the pads and the little holes directly behind the LCD and there was no continuity between pad 3 and it's corresponding circuit run to it's tiny ring...

On the spiffie schematic pad 3 is labeled as CONTR - it is recieved from the atmega... That would explain why all my continuity checks from the atmega to both sides of the header pin were good, I didn't check the back side of the LCD to their final destination..

What do you guys think?

[dcb]

good eye I'd blob some solder on there.

[Wingmn]

I tried blobbing solder on there, but it wouldn't flow all around the pad...

So, I ended up putting a jumper line between the little ring for pad 3 and Pin 3 on the other board... Continuity checked good, so I tested it out..

Still didn't work. Needless to say I did fix a problem. Just not the right problem.

I'm concerned that If I de solder that LCD too many more times I'm going to need a new one.. The pads are starting to deteriorate..

I'd like to fix this problem, so if anyone else has it they'll be able to learn from my mistakes

So, my next step is to go ahead and jumper wire all the atmega connections to the pads on the LCD by-passing the header.

I'll still have the header soldered in, but just in case a pin is broken the jumper wire will by - pass it... Unless anyone has a better idea - it's the best I can come up with.

dcb - thanks for the encouragement - I might end up buying a premade MPguino from you if I can't get mine fixed, it would be a shame not to use the wire's I spent hours tapping into my car (tapping, routing, etc)..

[Wingmn]

Here's an update!

I desoldered tonight tinned all my jumper wires before de soldering...

I soldered all 6 ( I already had the contrast on ) wires on the back of the atemga, I labeled them and my contrast (the one I had on there already ) broke off, so I thought great - good thing I tinned an extra wire, I'll just have to replace it..

I looked a little closer and found out I had put my contrast jumper wire on the little ring for pad 4, not 3....

I was PISSED. So - I was SOO sure that I found my problem I DE soldered all the jumper wires I had soldered and labeled on the back of the board.. I had yet to solder the other side to the LCD..

So, after taking out all my jumper wires - I re soldered the LCD to the board - put a new jumper wire on the head 3 pin and soldered it onto the top side pad 3.

SO.. Now I have a display.... YEAH... BUT... It's the top line of all blocks..

I re flashed the sketch - no change... - I did find out I could adjust the contrast and the brightness - but the solid top row of blocks is what I'm adjusting with the contrast...

somebody shoot me..

[Wingmn]

Anyone have any ideas about this new problem I have?

All blocks on top row of LCD - nothing on bottom row, brightness and contrast is adjustable.

I also did the serial check while it was hooked up to my PC and the 000.0 was scrolling in the Arduino program..

I am also able to upload sketches, but nothing changes whats on the display.

I did search through the forum for "blocks" but the other block problems did not seem like what I am experiencing.

Can someone tell me at least from the symptoms of what I've got if my atmega is still good or a bootloader got dropped.. I imagine if it did I couldn't load the sketch right? And the serial monitor wouldn't put anything out right? I mean I really don't know.

[wagonman76]

Can you get a voltage reading at the 5V power wire to the LCD? Pin 2 I think. That would at least tell you if you have any voltage issues. Mine would act up with anything below 4.9 volts and sometimes would show blocks on the screen, or clear itself, or restart, or lock up. I have read of quite a few others showing just blocks on the screen, for various reasons.

[Wingmn]

wagonman - I haven't checked to see what my voltage is on pin 2 of the LCD, I will though.

I'll take a look tonight before I desolder.

I did see several posts about blocks on the screen, perhaps I missed the one that was identical to my problem. *shrug* I'll look again.

[Wingmn]

Well - Here's my verdict.

I de soldered - re touched every solder connection that might have been considered grey - made a plastic backing for my LCD - resoldered everything because I thought maybe it was just the contact between boards -

And it still had blocks.............

wagonman - I did check pin 2 with power on - 5.06 v solid... So power was good I believe.

So - I desoldered again. Pushed all the pins down - removed/cut pins 7-10 off. Did not get the plastic off (I was to anxious to see if the new stuff worked). I cleaned up the remaining pins.

I recieved my NEW LCD today - blue background/white letters - made another plastic backing - soldered it into place - a bit more space between boards this time...

Plugged it into my car - and It WORKED!! HOT DOG!

It came up with Ver .74 - so I know I was re flashing the sketch correctly all those times. Mine shipped with ver .73 when I initially powered it up.

So, Either pushed the pins and cleaning them up solved the problem / or my LCD was toast... Considering all the times I've soldered and desoldered that LCD who knows..

Thanks gascort for sending your MPguino to dcb - thanks dcb for giving me 1 more thing to try before I stomped on my MPGuino

Hey - dcb - if you want I'll mail you my LCD if you are curious. I'm done soldering for a while.